Hydraulically-powered lifts are commonly used at maintenance facilities and service stations to lift buses, trucks, automobiles, and other types of motor vehicles. Lifting a motor vehicle is often necessary when performing service or maintenance operations such as tire or brake replacement, or tasks that require access to the underside of the motor vehicle.
Conventional hydraulic lifts typically comprise a hydraulic cylinder. The hydraulic cylinder includes a casing, and piston telescopically disposed within the casing. Pressurized hydraulic fluid is directed into the casing, so that the fluid acts against a first end of the piston. The force of the fluid on the piston causes the piston to extend from the casing. A superstructure suitable for engaging the motor vehicle can be mounted on the opposing end of the piston, so that extension of the piston from the casing urges the superstructure into the motor vehicle, and thereby lifts the motor vehicle.
The casing is typically located below the surface of the floor of the shop or service area, so that the piston can be retracted so as to place the superstructure at or near floor level when the vehicle. Positioning the superstructure in this manner is necessary to permit the motor vehicle to be driven or otherwise positioned over the superstructure. Thus, most or all of the casing must often be located at or below floor level. A relatively deep, e.g., ten-foot deep, trench or hole therefore may be required to accommodate the casing. The need for a relatively deep trench or hole can increase the cost and complexity of the installation, and can make it difficult or unfeasible to install a hydraulically-powdered lift in certain locations, e.g., where the water table or bedrock level is relatively shallow. Moreover, the structure required to support the casing is usually fixed and cast in concrete, with reinforcing bars, further adding to the cost and complexity associated with installing and removing the lift.
The amount of hydraulic fluid needed to operate the above-described lift can be relatively high, e.g., ninety gallons or more. The need to route relatively large amounts of pressurized hydraulic fluid through an underground casing generates a potential for contamination of the surrounding area caused by leakage of the hydraulic fluid. Moreover, the risk of ground contamination can be relatively high in applications wherein the unit that pressurizes and controls the flow of the hydraulic fluid is located within the trench or hole that accommodates the cylinder.